A Single-Phase Dynamic Voltage Restorer Based on Filterless Z-Source AC-AC Converter

In this paper, a single-phase dynamic voltage restorer (DVR) based on a Z-source AC-AC converter is proposed. The Z-source converter has a shared ground and continuous input current. Using the impedance network filter feature, the direct connection of the primary side of the injection transformer to the impedance network is provided. Therefore, the proposed system’s volume, weight, and cost are reduced due to the elimination of the input and output LC filter. The impedance network consists of a three-winding coupling inductor. Therefore, in addition to the duty cycle, the voltage injected by the DVR can be controlled by the coupled inductor turn ratios. Unlike conventional impedance source converter-based DVRs, the proposed DVR is able to compensate for a wide range of voltage sag and swell, even voltage sags of more than 50%. The proposed DVR is analyzed in different compensation and protection modes and simulation results are presented in PSCAD/EMTDC software to validate the calculated relationships and performance.